Pen holder base



FIG. 1 is a front elevational view of a pen holder base showing our new design;

FIG. 2 is a rear elevational view thereof;

FIG. 3 is a left side elevational view thereof;

FIG. 4 is a right side elevational view thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a bottom plan view thereof; and

FIG. 7 is a front perspective view thereof, the environmental structure shown in dotted lines being for illustrative purposes only. 

The ornamental design for a pen holder base, as shown and described. 